Surgical conditions in the gastrointestinal tract are often complicated by mucosal injury that results in the development of wounds or ulcers. For example, in ischemic and inflammatory bowel disorders, unremitting mucosal injury and ulceration are indications for surgical resection. Moreover, after surgical resection of bowel segments, resealing at anastomotic sites is required for reestablishing mucosal barrier function. Rapid resealing of mucosal wounds has been previously shown to occur by migration of epithelial cells, a process referred to as "restitution". During restitution, intestinal epithelial cells rapidly change shape with formation of cellular projections or lamellipodia at the leading edge. The overall aim of this proposal is to understand structural and molecular events associated with formation of lamellipodia and migration of intestinal epithelial cells during repair of intestinal mucosal wounds. We hypothesize that migration of intestinal epithelial cells during wound closure is driven by lamellipodial extensions at the leading edge and is dependent on dynamic cytoskeletal remodeling with modification of intercellular junctions. To test this hypothesis experiments have been proposed utilizing an in vitro model of wound resealing. The roles of actin regulating proteins in mediating F-actin restructuring in lamellipodial extensions of migrating intestinal epithelial cells will be examined in Specific Aim 1. In this aim, the effects of the motility factor, hepatocyte growth factor/scatter factor (HGF/SF) on cytoskeletal restructuring and migration of intestinal epithelial cells will also be analyzed. Specific Aim 2 determines the role of the Rho family of GTP binding proteins in mediating lamellipodial cytoskeletal remodeling and focal cell matrix associations in migrating intestinal epithelial cells. Rho function in intestinal epithelial cells will be examined by transfection studies to overexpress its function or by the use of inactivating toxins. Preliminary studies suggest that Rho proteins not only influence cell motility but also intercellular junctions of epithelial cells. Thus, Specific Aim 3 determines mechanisms by which Rho proteins and HGF/SF regulate such parameters in intestinal epithelial cells. Information obtained from these studies will provide insights into mechanisms of epithelial cell movement and rapid wound closure in the gastrointestinal tract. These studies should lay the foundation for developing novel strategies aimed at enhancing wound resealing after intestinal mucosal injury in surgical disease.